Diving method and apparatus



NOV. 5, 1968 J, CHATE ET AL 3,408,822

DIVING METHOD AND APPARATUS Filed Aug. 5, 1966 4 Sheets-Sheet 1 I "Illlllllll FIG. I

INVENTORS FREDERICK J. CHATE STEVEN A. T. KAPTEYN BY:%.H,MQQ JZ;

THEIR AGENT Nov. 5, 1968 F, J cHA-rg ET AL 3,408,822

DIVING METHOD AND APPARATUS Filed Aug. 5, 1966 4 Sheets-Sheet 2-INVENTOR'S:

FREDERICK J. CHATE STEVEN A. T. KAPTEYN 1BY= a THEIR AGENT Nov. 5, 1968J CHM-E ET AL 3,408,822

DIVING METHOD AND APPARATUS Filed Aug. 5, 1966 4 Sheets-Sheet 3 FIG. 5

INVENTORSI FREDERICK J. CHATE STEVEN A. T. KAPTEYN BYI I EIR AGENT Nov.5, 1968 F. J. CHATE ET DIVING METHOD AND APPARATUS 4 Sheets-Sheet 4Filed Aug. 5. 1966 F I G. 6

FIG. 8

F I G. 7

F I G. 9

INVENTORS:

CHATE FREDERICK J. STEVEN A. T. KAPTEYN BY: f

HE|R AGENT nited States ABSTRACT OF THE DISCLOSURE A method andapparatus for carrying out underwater operations with the aid of divingapparatus provided with at least a living compartment, a decompressioncompartment, a water-lock compartment and a working compartment. Thediving apparatus is lowered into the water to an operating depth atwhich a gas pressure approximately equal to the static water pressure atthe operating depth is maintained in the working compartment. Apredetermined substantially constant gas pressure higher thanatmospheric pressure and lower than the water pressure at the operatingdepth is maintained in th living compartment. Divers in the divingapparatus move periodically from the living compartment via thedecompression cornpartment to the working compartment and vice versa asgas and water is selectively supplied and discharged to and from thewater-lock compartment so as to maintain a desired pressure in thewater-lock compartment.

The invention relates to a method and diving apparatus for carrying outunderwater operations in particular to a depth of approximately 300meters.

It is known that in diving operations it is necessary to bring the divergradually from the water pressur at the operating depth back to theatmospheric pressure (decompression). This decompression istime-consuming, increasingly so as the water pressure at the operatingdepth becomes higher. The decompression time depends on the nature ofthe gas mixture breathed in by the diver, on the time spent by the diverunder the high pressure, and on the degree of the pressure exerted onthe diver.

In order to substantially shorten the time required for decompression itis advantageous not to decompress to atmospheric pressure, but to ahigher pressure viz. to an intermediate pressure lying betweenatmospheric pressure and the water pressure at the operating depth, forexample, to a pressure of 6 atma. The diver can remain at thisintermediate pressure in between the operations. Subsequentlycompression can be applied again, for example to 30 atma. whereupon thediver can continue his activities. This work period can, if desired, befollowed on one or more occasions by decompression to the intermediatepressure, a rest period at the intermediate pressure, compression and afollowing work period.

The object of the invention is to provide a method and diving apparatusby means of which the operations may be carried out in the mannerdescribed above.

The invention, therefore, relates to a method for carrying outunderwater operations with the aid of a diving apparatus provided with aliving compartment, a decompression compartment, a water lockcompartment and a working compartment, in which method the divingapparatus is lowered into the water to a certain depth (operating depth)at which depth a gas pressure approximately equal to the static waterpressure at the operating depth is maintained in the workingcompartment, a gas pressure higher than atmospheric pressure and lowerthan the water pressure at the operating depth is maintained in theliving compartment, and divers present in the diving apparatus moveperiodically from the living compartment via atent the decompressioncompartment and the water lock compartment to the working compartment,and vice versa, the divers carrying out the desired operations, forexample on an oil or gas well in the sea bottom, in the workingcompartment.

The invention moreover relates to a diving apparatus comprising a livingcompartment, a decompression compartment, a water lock compartment and aworking compartment, scalable manholes between the said compartments,means for controlling the gas pressure in the working compartment, meansfor maintaining in the living compartment a suitable breathing gasmixture having a pressure higher than atmospheric and lower than thestatic water pressure at operating depth, means for controlling the gaspressure in the decompression compartment, and means for supplying ordischarging gas or water having a desired pressure to or from the waterlock compartment.

In order to ensure that the operations to be carried out underwaterproceed as smoothly and efficiently as possible, it is desirable for asupervisors compartment to be present also, in addition to means formaintaining in the supervisors compartment a suitable breathing gasmixture at approximately atmospheric pressure. From this supervisorscompartment supervisory personnel can control, guide and direct theoperations to be carried out by the divers, the said supervisorypersonnel working under conditions of normal pressure and normal air inthe supervisors compartment.

The invention will now be elucidated with reference to the diagrammaticdrawing in which FIGURE 1 shows a lateral view of a longitudinal sectionof the diving apparatus;

FIGURE 2 shows a top-plan view of a cross-section BB of the divingapparatus;

FIGURE 3 shows a top-plan view of a cross-section AA of the divingapparatus;

FIGURE 4 shows a top-plan view of the diving apparatus;

FIGURE 5 shows a fragment of a lateral view of a longitudinal section CCof the diving apparatus;

FIGURE 6 shows a fragment of a bottom-plan view of the diving apparatus;

FIGURE 7 shows a lateral view of a longitudinal section DD of the divingapparatus;

FIGURE 8 shows a top-plan view of a cross-section EE of the divingapparatus;

FIGURE 9 shows a fragment of a lateral view of a longitudinal sectionF-F of the diving apparatus.

The diving apparatus according to the invention comprises asubstantially bell-shaped working space 1, substantially bounded by apreferably cylindrical side wall 2, a wall 3 connecting to this latteron the upper side, having the shape of part of a torus surface, and anupper wall 4, the bottom side being left open. In the upper wall 4 ahole 5 is arranged, preferably excentrically. To this a pipe 6, providedwith an upper wall 7, is connected in order to increase the usefulworking space. The working space present in the pipe 6 is indicated bythe reference numeral 8. To the upper end of the cylindrical side wall2, a hollow torus-shaped element '9 is secured, for example, by means ofa welded joint. A part of the wall of this torus-shaped element 9 formsthe said wall 3 of the working space 1. A number of substantially radialbulkheads 12, 13, 14, 15, shown in FIGURE 2, divide the torus-shapedelement into a supervisors compartment 16, a living compartment 17, adecompression compartment 18 and a water-lock compartment 19,respectively.

A second cylindrical side wall 21 (FIGURES l and 3) is arranged round,and at some distance from the cylindrical side wall 2, so that anannular space is formed between the two side walls 2 and 21, which spaceis divided by means of radial bulkheads 22, 23, 24, 25, 26, 27,

28 and 29 into compartments indicated by the reference numerals 31, 32,33, 34, 35, 36, 37, and 381 respectively. In the lower part of the saidannular space are situated three trimming tanks 39 and ballast 40 (seeFIGURE 9). In the compartments 32, 34 and 37 are guide means which willbe discussed later. Compartment 31 serves as a passage through which thedivers can pass from the water-lock compartment 19 to the working space1, and vice versa. For this purpose a ladder 41 is arranged in thecompartment 31. Between the water-lock compartment 19 and thecompartment31 is a door 44, through which divers can pass'from the compartment 19to the compartment 31 and vice versa. The compartment 31 is providedwith a door 42 in the wall 21, which leads outside. The main power plantand instruments (not shown) are situated in the compartment 33 and inthe compartment 35 there is a hydraulically operated winch 43 andancillary equipment (not shown) for carrying out work on a well on thesea bottom. In the compartment 36 are arranged the required electricbatteries (not shown) and in the compartment 38 the water pumps and thetrimming pump (not shown).

In the supervisors compartment 16 are arranged the controls, forexample, for controlling the gas mixtures, for controlling gaspressures, for controlling the diving bells buoyancy, for operating thewater-lock compartment, for operating the winch, for operating andcontrolling the diving apparatus propulsion equipment (not shown). Thesupervisors compartment 16 also contains emergency controls, lightingsystems, intercommunication systems and power plants (not shown). Thesupervisors compartment 16 is provided on the upper side with a door 45,while the radial bulkheads 12 and 13 are likewise equipped with doorsindicated by the reference numerals 46 and 47, respectively. These doors45, 46 and 47 serve inter alia to facilitate escape in emergencies. Alldoors 45, 46 and 47 are provided with portholes, indicated by thereference numerals 49, 50 and 51, respectively. The portholes 50 and 51(FIGURE 1) are necessary for inspecting the water-lock compartment 19and the living compartment 17, from within the supervisors compartment16. The porthole 49 (FIGURE 4) in the door 45 serves for checking, afterthe diving apparatus has been hauled up, whether the diving bell isfully above water so that the door 45 can be opened without the risk offlooding the supervisors compartment 16.

A number of portholes are arranged in the walls of the supervisorscompartment 16, viz. a number, indicated by the reference numeral 54, onthe inside, and a number indicated by the reference numeral 55 on theoutside. The

portholes 54 on the outside are used for navigational purposes, andthose on the inside for use in carrying out operations on the seabottom, for example, work on a well in the seabed. All pipes and cablesare passed into the supervisors compartment 16 through at least oneaperture (not shown) in the wall of the supervisors compartment, whichaperture is preferably arranged on the bottom side or the inner side ofthe supervisors compartment 16, in order to reduce the risk of damage toa minimum. Cable or pipe connections between the compartments in thehollow torus-shaped element 9 are passed through openings in the radialbulkheads in the element 9.

The living compartment 17 (FIGURE 7) is provided on the upper side witha door 56 in which a porthole 57 is arranged. As explained already,radial bulkhead 13 (FIGURE 1) contains the door 47, which providesaccess to supervisors compartment 16 from the living compartment 17, andvice versa. In the radial bulkhead 14 (FIG- URE 2) is a door 58, whichprovides access to the decompression compartment 18- from the livingcompartment 17, and vice versa. A porthole 59 is arranged in the door58. Portholes are also arranged in the wall of the living compartment17, viz. portholes 60 on the outside and portholes 61 on the inside.

In the radial bulkhead 15 (FIGURE 2) is a door 65,

which provides access to the water-lock compartment 19 from thedecompression compartment 18 andvice versa, A porthole 66 is arrangedinthe door 65. The decompression compartment 18 contains, for example,compressors for breathing equipment and a compressorfor dischargingoxygen-helium to above the surface of the water (not shown). Thesecompressors are operated from the supervisors compartment 16;appurtenant valves (not shown) can, however, be hand-operated in thedecompression com,-,

partment 18, a feature which can be of importance in emergencies.

The supervisors compartment 16, the living compartment 17 and thedecompression compartment 18 are pref.-

erably insulated with heat-insulating material, for example, glass woolcovered for Formica.

The door 44 (FIGURE 2) provides access to partment 31 from water-lockcompartment 19 and vice versa. In the water-lock compartment 19 arearranged, telephone connections and a breathing manifold. The. breathingcontrol valves are provided with remote control, but if necessary theycan be hand-operated from within the water-lock compartment, which maybe desirable in the case of emergencies.

The compartment 35 is provided with a door 67 (FIG- URE 1), providingaccess to the working space 1, through 118, for example, nitrogen,oxy-helium and oxygen cyl-.

inders, are stored.

With reference to FIGURE 1, the reference numeral 68 indicates theconventional well head, presenton the sea bottom 69, of a well drilledin the sea bottom 69 (oil or gas well). The reference numerals 70 and 71respectively indicate the conventional inside and outside tubes of thewell. The well head can be equipped with conventional blow-outpreventers 72. The well head 68v is provided with a steel framework 73,which is rigidly secured to the well head 68 by means of a supportingstructure 74 and guide rods 75. The guide rods 75 are provided at theirupper ends with a conical part 76 (FIG- URE 5). To the conical part 76of each guide rod 75 an appropriate guiding cable 77 is secured, whichcables lead vertically upwards to a ship (not shown). The divingapparatus according to the invention is provided with a number of cableducts 7-8, for instance three. Each duct 78 is preferably provided witha bush 79, through which a cable 77 is passed. The upper side of divingapparatus is provided with cable cutters 81, each of which grips roundthe cable 77, and which can be used in emergenciesto cut through thecables 77. For the sake of clarity only one cable cutter 81 is shown inFIGURE'4. It should be noted that the guide cables can be omitted ifdesired. In

this case the diving apparatus is directed only by accurate maneuveringwith the aid of propellers which can befastened to the diving'apparatus.

A number of funnel-shaped elements 80, which can grip round the guiderods 75, are arranged against'the outer side of the lower part of thewall 2 of the working space 1.

In addition to the guide system described above the diving apparatus isalso provided with three propellers '84, arranged on the same levelalong the Wall 21 at equal distances from one another. Only one of thesepropellers is shown in the drawing (FIGURE 5). Each propeller 84 ispowered by a reversible hydraulic motor 85, the speed of which can becontrolled by means of a flow 'control valve (not shown). Each propeller84 gives a horizontal force, the magnitude of which is determined by therota tional speed of the propeller. By means of the said three thecompropellers 84 and accurate controlling of the speed of each propeller84, the diving apparatus can be propelled through the water in anydesired horizontal direction and, moreover, rotated around its verticalaxis.

The diving apparatus is also provided with a propeller 86 for moving thediving apparatus in a vertical direction, which propeller 86 is poweredby a reversible and adjustable hydraulic motor 87. This propeller 86 andmotor 87 are secured to the outside of the pipe 6 (FIGURES 1 and 4). Bycontrolling the buoyancy of the driving apparatus in such a way that theapparatus is suspended in the water it is possible, by means ofpropeller 86, to obtain a closely controlled vertical movement of thediving apparatus. In the'event that there is a breakdown in the supplyof nitrogen to the diving apparatus this propeller 86 can be of usesince it can be brought into action immediately to compensate for theloss in buoyancy caused by the said breakdown.

It is possible to secure to the diving apparatus a safety cable attachedto the ship in order to be able to hoist the diving apparatus out of thewater in case of emergency, but a cable of this type is preferably notused so as to prevent the ships movements from being transferred to thediving apparatus. A hose or cable 88, leading to the ship, is secured atthe upper side of the pipe 6. This cable 88 serves for the supply ordischarge of gas and/or electricity. There are, for example, two ofthese cables 88 present (see FIGURE 4).

The diving apparatus is kept in an upright position by pumping waterballast between three trimming tanks by means of a pump.

A point of light 89, which acts as a beacon, is preferably arranged onthe upper wall 7 of pipe 6.

The buoyancy of the diving apparatus is controlled by means of a liquidlevel controller (not shown), which regulates the water level in thespace 8, in such a way that the diving apparatus always possesses thecorrect buoyancy.

The diving apparatus is provided with an anchoring system for anchoringthe diving apparatus firmly to the steel framework 73. This anchoringsystem comprises three cylinders 91 arranged at equal distances fromeach other along the inner side of the wall 22 and each containing apiston (not shown), to which a rod 92 is attached bearing a lockingdevice 90 at the end. The steel framework 73 is provided with threeslots 93 arranged at equal distances from each other, each of which caninterlock with a locking device 90. Once the diving apparatus has beenlowered onto the steel framework 73, the rods 92 are driven downwards bymeans of pressure fiuid which is compressed behind the pistons in thecylinders 91. The rods 92 then slide into the appropriate slots 93.After the rods 92 have been pushed into the slots 93 the locking devices90 are forced hydraulically in a radial direction outwards so that theygrip behind the bottom side of the steel framework 73, whereuponpressure fluid is compressed behind the other sides of the pistons intothe cylinders 91 so that the rods 92 are driven upwards to some extentwith the result that a rigid connection is obtained and the divingapparatus is thus anchored firmly to the steel framework 73.

The ballast of the diving apparatus consists of three iron ballastplates 94. Each ballast plate 94 is equipped with three supports. One ofthe supports is a hook 95, which grips round a pin 100 on the ballastplate 94, which hook 95 is hingeable round a hinge 96. A breaking pin 97holds the hook 95 in the correct position. If it is desired to dischargethe ballast the breaking pin 97 can be broken by means of ahydraulically powered piston 98 moving in a cylinder 99. If it is notpossible to break the breaking pin 97 by means of the piston 98 andexplosive charge can be used to break the breaking pin 97. Once the pin97 has been broken the hook 95 will swing around the hinge 96 with theresult that the pin 100 will leave the hook 95 and the ballast plate 94will fall freely downwards.

In order to facilitate steering the diving apparatus under the water thesuperivsors compartment 16 is provided with two water levels arrangednormal to each other, with a meter for measuring the speed in a verticaldirection, comprising a Pitot tube and a depth gauge (not shown).

The operation of the diving apparatus described above will now bediscussed. Let it be assumed that the diving apparatus is situated ondeck of a ship (not shown), which is lying approximately above the pointon the sea bottom where it is desired to carry out certain operations.Let it be assumed for example that certain operations have to be carriedout on an oil or gas well in the sea bottom, or that certain opertaionshave to be carried out at a well head 68 of such a well.

The diving apparatus is lowered into the water from the ship for exampleby means of a crane. Owing to the fact that the working space 8 in thepipe 6 is filled with gas for example nitrogen, as is the enclosed space117, the diving apparatus will remain floating on the Water in such amanner that it will extend a considerable distance above the surface ofthe water. The supervisors will now board the diving apparatus through adoor 45 on the upperside of the supervisors compartment 16, whereuponthe door 45 is hermetically sealed. For safety reasons there willnormaly be at least two supervisors present in the supervisorscompartment 16. In orderto ensure that the supervisors are able to workunder the most favorable conditions the supervisors compartment 16 iskept filled with air at atmospheric pressure. The task for one of thesupervisors is to supervise the operations as a whole and moreover tosteer the diving apparatus. The other supervisor has the task ofsupervising the respiration mixtures and observing the movements of thedivers.

At the moment when the supervisors enter the diving apparatus the divers(at least two in number) are already present in the living compartment17, which is kept filled at all times with a suitable breathing gasmixture, for example a mixture of oxygen and helium, at a pressurehigher than atmospheric, for example approximately 6 atma. If the diversare not yet present they can enter the living compartment 17 via thedoors 42 and 44, the water-lock compartment 19, door 65, decompressioncompartment 18 and door 58. In this latter case they will require anaqualung or temporary air supply through a hose. The divers thereforefinally arrive in the living compartment 17, and if desired the doors 58and may be open. The water-lock compartment 19, decompressioncompartment 18 and living compartment 17 thus communicate with eachother while in all these compartments 17, 18 and 19 a suitable breathinggas mixture, for example a mixture of oxygen and helium, is present at apressure of approximately 6 atma.

One of the supervisors subsequently opens a valve (not shown) in theupper part of the working space 8 in the pipe 6, and a water supply tothe enclosed space 117, whereupon the diving apparatus begins to sink asa result of the water entering the spaces 8 and 117. As soon as thediving apparatus is just below the surface of the water the buoyancy ofthe diving apparatus is so adjusted as to ensure that it is still justpositive. The propeller 86 is now activated so that the diving apparatusbegins to move downwards as a result of the action of the propeller 86.

While moving downwards the diving apparatus is guided'by the guidecables 77 which are stretched vertically between the ship and the wellhead 68. While the diving apparatus is proceeding downwards the diversenter the decompression compartment 18 from the living compartment 17,whereupon they hermetically seal the door 58 between these 2compartments. The pressure in the decompression compartment 18 and thewater-lock compartment 19 is now gradually raised by the supply, forexample from the ship, of for example oxygen and helium. The pressure israised until it is equal to the water pressure at the depth where thedesired operations are to be carried out, for example equal to the waterpressure in the neighborhood of the well head 68. Thus, if the waterpressure near the well head 68 is 32 atma., the pressure in thedecompression compartment 18 and the Water-lock compartment 19 will begradually raised from 6 to 32 atma. One of the supervisors in thesupervisors compartment 16 keeps a constant check on the correctcomposition of the helium/oxygen mixture and corrects it whenevernecessary.

Once the diving apparatus has reached the well head 68 one of thesupervisors brings the horizontal propellers 84 into operation in orderto counteract the influence of horizontal currents. The funnel-shapedelements 80 receive the guide rods 75 and the diving apparatus movesdown the guide rods 75 until it comes to rest on the steel framework 73.One of the supervisors then set the anchoring system in motion, is. thesupply of pressure fluid to cylinders 91 causes the rods 92 to moveaxially downwards in such a way that the ends thereof interlock with theslots 93, whereupon the supply of pressure fluid causes the lockingdevices 90 to move radially outwards, and finally the rods 92 are movedupwards to some extent so that the diving apparatus is firmly anchoredto the steel framework 73.

The working spaces 1 and 8 are now further filled with nitrogen so thatthe water is completely displaced from these spaces. Since it isassumed, as stated above, that the water pressure at the well head 68has a value of 32 atma. the pressure of the nitrogen in the workingspaces 1 and 8 will also have to be 32 atma.

While the diving apparatus is being anchored to the steel framework 73the divers leave the decompression compartment 18 and enter thewater-lock compartment 19, whereupon they hermetically seal the door 65behind them. As stated above, the water-lock compartment 19 contains amixture of helium and oxygen at a pressure of 32 atma. which mixture isbreathed in by the divers.

The breathing compressors are now started by the supervisors and thedivers put on their working suits and helmets, whereupon they breath ina suitable respiratory mixture of for example oxygen and helium at 32:atma. The divers now sit down on a seat 107, to which they strap themelves. One of the supervisors in supervisors compartment 16 now starts awater pump (not shown), in order to fill the water-lock compartment 19with water. In addition he activates a compressor (not shown), whichpasses the oxygen/helium mixture through a line from the water-lockcompartment 19 to the decompression compartment 18, from where it flowsthrough a line to the ship.

While the water-lock compartment 19 is being filled with water thedivers check that their helmets are operating properly and that thetelephone connections present are functioning correctly. If theydiscover any leak they press a button which passes a signal to thesupervisors indicating that the filling of the water-lock compartment 19with water must be stopped. One of the supervisors in the supervisorscompartment 16 observes the divers in the water-lock compartment 19 viaportholes between the supervisors compartment 16 and the water-lockcompartment 19. As soon as the water-lock compartment 19 is completelyfilled with water the latter flows over via lines 120 and 121 to asignal tank (not shown), which is arranged, for example in supervisorscompartment 16, whereupon the supervisor stops the water pump. Theconneeting line 121 is then closed by means of a valve 126, and a line122 connecting with the working space 8 is opened by means of a valve125, so that the water in the water-lock compartment 19 is displaced bynitrogen from the working space 8, the water flowing off to the outsidethrough a line 123, which is provided with a valve 124. It should benoted that the valves 124, 125 and 126 can be provided with remotecontrol and can also be situated outside the water-lock compartment 19.Once all the water has been displaced from the water-lock compartment 19only nitrogen having the same pressure as the nitrogen in the workingspace 1, i.e., 32 atma., remains in the water-lock compartment 19. Thedivers invariably breathe in through their masks a mixture of forexample oxygen and helium having a pressure of 32 atma. Once thewater-lock compartment 19 has been completely filled with nitrogen thedivers open the door 44 and from the water-lock compartment 19 entercompartment 31, which serves as a passage, via the ladder 41.

From compartment 31, the divers enter the working space 1 after havinglowered a hydraulically operated working platform (not shown) into theworking space 1. As already stated compartment 35 contains ahydraulically powered and controlled winch 43, together with auxiliaryequipment (not shown). In addition, compartment 35 also contains acounter wheel 127, which serves to determine the amount of cable 109payed out from the winch 43. The cable 109 is passed through a rubbergasket (not shown) in the door 67. The compartment 35 is normally filledwith nitrogen which is held at a pressure approximately equal to thewater pressure at the level at which the operations are being carriedout.

The divers who are now in working space 1, now equalize the gaspressures in compartment 35 and working space 1, whereupon they open thedoor 67. The cable 109 is now loosened from the door 67, and a so-calledlubricator 110, by means of which the desired operations, known per se,at the well head can be carried out, is secured to the end of the cable109, which is passed over pulley 111. Measuring equipment in thesupervisors compartment 16 indicates the weight borne by cable 109 andthe amount of cable 109 payed out. The supervisors in the supervisorscompartment 16 can regulate the speed and direction of rotation of thewinch 43 and can apply a band brake (not shown) in order to permit theequipment to remain suspended at a given depth in the well for a longerperiod of time.

After the operations with the lubricator 110 have been carried out thelubricator 110 is disconnected and fixed in a clamp 114. Subsequently,the cable 109 is passed again through the door '67 whereupon the latteris hermetically sealed.

With the aid of the correct equipment the divers, working in cooperationwith the supervisors, who are invariabily present in the supervisorscompartment 16 can carry out all kinds of operations, known per se, atthe well. Since these operations are known per se, they will not bediscussed in any further detail here. For the purposes mentioned allkinds of equipment may be carried in the working spaces 1 and 8, forexample another winch (not shown). By the way of example a tool rack 112with the appropriate tools 113 is shown in the drawing.

It is to be noted that the diving apparatus described above is not onlysuit-able for carrying out operations on underwater oil or gas wells,but is also suitable for carrying out other underwater operations. Thedivers who are provided, via their masks, with a mixture, for example ofhelium and oxygen having a pressure equal to the water pressure at thelevel at which the divers carry out their operations, can, if desired,also enter the water outside the working space 1 and carry out anyoperations required in the water in the neighborhood of the divingapparatus.

At a given moment the divers will wish to return from the working space1 to the living compartment 17. For this purpose they leave the workingspace 1 and enter water-lock compartment 19 via compartment 31 and door44. After the divers have entered water-lock compartment 19 they sealthe door 44 hermetically behind them. The supervisors present insupervisors compartment 16 activate a water pump (not shown) so thatwater is passed into the water-lock compartment 19, and this displacesthe nitrogen from water-lock compartment 19 into the working space 1. Assoon as the water-lock compartment 19 is completely filled with water,the water pump is stopped, whereupon the oxygen/helium connec- 9 tion121 with the decompression compartment 18 is elfected, the supply ofoxygen/helium to the decompression compartment 18 is opened, and thewater discharge line from the water-lock compartment 19 is opened. As aresult the water-lock compartment 19 is filled with an oxygen/heliummixture with a pressure of 32 atma. which displaces the water from thewater-lock compartment 19. After all the water has been displaced fromthe water-lock compartment 19, the divers remove their masks and workingsuits, whereupon they breathe in the oxygen/helium mixture of 32 atma.directly from the water-lock compartment 19. The divers leave theirmasks and working suits behind in the water-lock compartment 19, openthe door 65 and enter the decompression compartment 18. In thedecompression compartment 18 there is likewise a mixture of oxygen andhelium havin a pressure of 32 atma., and this the divers freely breathein.

The supervisors present in supervisors compartment 16 now start acompressor which causes the pressure of the oxygen/helium mixture tofall very gradually from the original value of 32 atma. to 6 atma. Thisdecompression must be effected very gradually in order to ensure thatthe divers suffer no harmful consequences to their health. For thisreason the supervisors invariably watch the divers during thedecompression by means of television equipment (not shown). Once thepressure of 6 atma. has been reached in the decompresion compartment 18the compressor is stopped and the divers proceed via door 58 to theliving compartment 17 where they can rest, if required, and recoverand/or have something to eat. Food is available in the livingcompartment 17 in containers which have been brought to the same pressure as the pressure prevailing in the living compartment 17. Ifnecessary, the divers can proceed after some time in the mannerdescribed to the working space 1 in order to continue the operation,after which they can return in the manner described to the livingcompartment 17. If necessary, this pattern of proceeding from livingcompartment 17 to working space 1, carrying out of perations there,returning to living compartment 17, and resting in living compartment 17can be repeated a relatively large number of times.

The great advantage of moving from the working space 1. where theprevailing pressure is 32 atma., to living compartment 17, where theprevailing pressure is 6 atma., is that decompression takes considerablyless time if it only has to be effected to a pressure higher than 1atma., for example 6 atma., and not to l atma.

After the operations have been entirely completed and the divers haveproceeded to the living compartment 17, in which they breathe indirectlyan oxygen/helium mixture at a pressure of 6 atma., it may be necessaryto raise the diving apparatus again to the surface.

For this purpose the supervisors, present in supervisors compartment 16,open the valve (not shown) mentioned above, in the upper part of pipe 6.The result of this is that nitrogen escapes from the working spaces 1and 8 and that the water flows into the working spaces 1 and 8. Thequantity of water flowing into the working spaces 1 and 8 is socontrolled that the diving apparatus is given a slightly negativebuoyancy. The supervisors subsequently hydraulically operate theanchoring system in such a way that the rods 92 are moved downwards tosome extent, whereupon the locking devices 90 are drawn inhydraulically. The rods 92 are subsequently displaced hydraulically inan upward direction out of the slots 93, with the result that the divingapparatus is disconnected from the platform 73. The diving apparatus issubsequently moved upwards, either by means of the propeller 86, or bygiving the diving apparatus a comparatively slight positive buoyancy byremoving a small quantity of water from the working spaces 1 and 8.While the diving apparatus is being raised the funnel-shaped elements 80move upwards along the guide rods 75 and subsequently leave them. Thediving apparatus now moves gradually upwards along the guide cables 77to the surface of the water.

Once the diving apparatus has reached the surface of the water it ishoisted on board the ship. If desired the supervisors can then leave thesupervisors compartment 16 via door 45. If desired, the divers canremain in the living compartment 17 until the diving apparatus islowered again for a subsequent descent. In order to give the diverssufficient room to move around, the doors 58 and 65 may remain open.Food may be supplied to the divers in closed containers which have beenbrought to the pressure prevailing in the living compartment 17, forexample 6 atma. In order to pass the food containers into the livingcompartment 17 from outside use is made of the water-lock compartment19, which serves as a shuttle.

If the divers wish to leave the diving apparatus they enter thedecompression compartment 18, whereupon the doors 58 and 65 are closed.The pressure in the decompression compartment 18 is thereupon graduallyreduced to atmospheric pressure. The pressure in the water-lockcompartment 19 is also reduced to atmospheric pressure. The divers thenopen door 65, enter water-lock compartment 19, open the door 44 andproceed 'by ladder 41 into compartment 31, whereupon they leave thediving apparatus via door 42.

It is to be noted that the decompression compartment 18 and thewater-lock compartment 19 can, if desired, be interchanged, so that thewater-lock compartment 19 is adjacent to the living compartment 17 andthat the decompression compartment 18 is adjacent to the supervisorscompartment 16.

We claim as our invention:

1. A method for carrying out underwater operations with the aid of adiving apparatus provided with a living compartment, a decompressioncompartment, a waterlock compartment and a working compartment, whichdiving apparatus is lowered into the water to a certain depth (operatingdepth), at which depth a gas pressure approximately equal to the staticwater pressure at the operating depth is maintained in the workingcompart ment, a predetermined substantially constant gas pressure higherthan atmospheric pressure and lower than the water pressure at theoperating depth is maintained in the living compartment, and diverspresent in the diving apparatus move periodically from the livingcompartment, via the decompression compartment and water-lockcompartment to the working compartment and vice versa while selectivelysupplying and discharging gas and water to and from said water-lockcompartment so as to maintain desired pressure therein, the diverscarrying out the desired operations in the working compartment as itsurrounds at least the top of an underwater well installation near thesea bottom.

2. A diving apparatus for carrying out underwater operations, comprisinga living compartment, a decompression compartment, 2. water-lockcompartment and a Working compartment, sealable manholes between thesaid compartments, means for controlling the gas pressure in the Workingcompartment, means for maintaining in the living compartment a suitablebreathing gas mixture, having a predetermined substantially constantpressure higher than atmospheric and lower than the static waterpressure at the operating depth, means for controlling the gas pressurein the decompression compartment and means for selectively supplying anddischarging gas and water having a desired pressure to and from thewaterlock compartment.

3. A diving apparatus as claimed in claim 2, characterized in that theworking compartment is situated in a substantially bell-shaped element.

4. A diving apparatus as claimed in claim 3, characterized in that asupervisors compartment is present and includes means for maintaining asuitable breathing gas mixture of approximately atmospheric pressure inthe supervisors compartment.

5. A diving apparatus as claimed in claim 4, characterized in that asealable manhole is present between said supervisors compartment andsaid living compartment.

6. A diving apparatus as claimed in claim 2, characterized in that theliving compartment, decompression compartment and water-lock compartmentare arranged in a hollow torus-shaped body.

7. A diving apparatus as claimed in claim 6, characterized in that asupervisors compartment is present and is also arranged in the saidhollow torusshaped body.

8. A diving apparatus as claimed in claim 7, characterized in that theend walls of the said living compartment, decompression compartment,water-lock compartment and supervisors compartment consist of radialbulkheads arranged in the hollow torus-shaped body.

9. A diving apparatus as claimed in claim 6, characterized in that theworking compartment is situated in a substantially bell-shaped elementand the hollow torusshaped body is on the upper side of thesubstantially bell-shaped element serving as a working compartment.

10. A diving apparatus as claimed in claim 2, characterized in that thebottom side of said diving apparatus is provided with anchoring meansfor anchoring said apparatus to an underwater installation.

11. A diving apparatus as claimed in claim 10, characterized in that theanchoring means are provided with hydraulic controls.

12. A diving apparatus as claimed in claim 2, characterized in that saidapparatus is provided with guide means adapted to cooperatively engagecable guide means eX- tending from an underwater installation to thesurface.

13. The apparatus of claim 2 wherein all of said cornpartments are inclose proximity to each other.

References Cited DAVID J. WILLIAMOWSKY, Primary Examiner.

J. K. BELL, Assistant Examiner.

